A pilot study demonstrating cardiac uptake with 18F-florbetapir PET in AL amyloidosis patients with cardiac involvement.

18F-florbetapir is a promising tracer in amyloidosis. This study evaluates its use in patients with systemic AL amyloidosis (AL) before and after treatment as well as its serial utility in monitoring. Fifteen AL patients with cardiac involvement underwent 18F-florbetapir PET imaging and three patients underwent repeat imaging after chemotherapy. All patients had demonstrable cardiac uptake with 18F-florbetapir. Cardiac uptake appeared greater in chemotherapy-naïve vs. chemotherapy-established AL patients median (left ventricular retention index 0.21 vs. 0.14 min-1, respectively) and greater in patients that had not achieved at least a partial haematological response (left ventricular retention index 0.2 vs. 0.14 min-1, respectively). There was no interval difference in cardiac uptake and no correlation in cardiac uptake with cardiac biomarkers or serum free light chains. This is the largest study of 18F-florbetapir in patients with AL amyloidosis. It is the first study to include patients prior to starting chemotherapy and uniquely includes patients who underwent repeat imaging after chemotherapy. All patients had cardiac uptake with 18F-florbetapir, regardless of haematological or NT-proBNP response to chemotherapy. There was a suggestion that treatment-naïve patients may have higher cardiac uptake. Larger studies are required to establish the role of this tracer in screening patients with amyloidosis for cardiac involvement, discriminating between ATTR and AL amyloidosis, and in disease monitoring.

Patient-specific optimisation of administered activity and acquisition times for 18F-FDG PET imaging.

BACKGROUND: The purpose of this study is to identify a method for optimising the administered activity and acquisition time for 18F-FDG PET imaging, yielding images of consistent quality for patients with varying body sizes and compositions, while limiting radiation doses to patients and staff. Patients referred for FDG scans had bioimpedance measurements. They were injected with 3 MBq/kg of 18F up to 370 MBq and scanned on a Siemens Biograph mCT at 3 or 4 min per bed position. Data were rebinned to simulate 2- and 1-min acquisitions. Subjective assessments of image quality made by an experienced physician were compared with objective measurements based on signal-to-noise ratio and noise equivalent counts (NEC). A target objective measure of image quality was identified. The activity and acquisition time required to achieve this were calculated for each subject. Multiple regression analysis was used to identify expressions for the activity and acquisition time required in terms of easily measurable patient characteristics. RESULTS: One hundred and eleven patients were recruited, and subjective and objective assessments of image quality were compared for 321 full and reduced time scans. NEC-per-metre was identified as the objective measure which best correlated with the subjective assessment (Spearman rank correlation coefficient 0.77) and the best discriminator for images with a subjective assessment of "definitely adequate" (area under the ROC curve 0.94). A target of 37 Mcount/m was identified. Expressions were identified in terms of patient sex, height and weight for the activity and acquisition time required to achieve this target. Including measurements of body composition in these expressions was not useful. Using these expressions would reduce the mean activity administered to this patient group by 66 MBq compared to the current protocol. CONCLUSIONS: Expressions have been identified for the activity and acquisition times required to achieve consistent image quality in FDG imaging with reduced patient and staff doses. These expressions might need to be adapted for other systems and reconstruction protocols.

Quantitative (99m)Tc DTPA renal transplant scintigraphic parameters: assessment of interobserver agreement and correlation with graft pathologies.

Various (99m)Tc DTPA scintigraphic quantitative parameters for renal graft function assessment have been recommended, but none is universally accepted. In this study, 439 dynamic renal transplant scintigraphies (DRTS) were retrospectively analysed. In the first set of studies, four observers analysed the 47 random DRTS and interobserver agreement of eleven derived parameters was assessed. In the other set of studies, 181 instances of DRTS, performed on 127 recipients with renal biopsies within five days of each other were selected for correlation with pathology. Hilson's Perfusion index (HI), ΔP, P:Pl, P:U & T10 were selected for this analysis. The pathologies were categorized into renal vascular compromise (RVC; n = 20), acute tubular necrosis (ATN; n = 40), vascular rejection (VR; n = 34), interstitial rejection (IR; n = 33), normal (NOR; n = 36) and unclassified pathologies (n = 18). A majority of the parameters showed good Intraclass correlation (ICC). HI differentiated well between grafts with RVC and the remainder of the study cohort, (p < 0.0001; AUC = 0.84); at a cut-off > 278, it had 84% sensitivity and 78% specificity (Likelihood ratio = 3.8). At < 278, it had 98% 'negative' predictive value for RVC. HI also showed reasonable association with VR (p = 0.02; AUC = 0.62) and IR (p = 0.009; AUC = 0.65). However, significant overlap of HI values between various subgroups was noted. Other parameters had good ICC but were not effective in differentiating graft pathologies. Of the measured parameters, only HI proved to be useful for the pathological assessment, particularly in the identification of vascular compromise. This parameter, however, has lower specificity in differentiating the other pathologies.

Thermal control of brown adipose tissue in 18F-FDG PET.

UNLABELLED: The visualization of hypermetabolic brown adipose tissue (BAT) on (18)F FDG PET lowers the efficacy of PET and has been linked with the environmental temperature of the patient before presentation. The objective of this paper is to investigate the effectiveness of thermal control on BAT and (18)F-FDG PET. METHODS: Three hundred patients undergoing (18)F-FDG PET were defined by 1 of 2 groups. Group A consisted of 150 consecutive patients from August to October 2009 (spring). Group B consisted of 150 consecutive patients from December to February 2010 (summer). In addition to normal preparation, group B received instructions to dress warmly and was warmed during the uptake period of their scan. Images were assessed for the presence of BAT. Standardized uptake value data were collected and compared. RESULTS: BAT was present in 9.3% of patients; 15.3% of patients that were not warmed (group A) demonstrated BAT, and this was reduced to 3.3% in the group that underwent warming (group B) (P = 0.0005). BAT was more common in men (10.9%) than women (6.8%), and women responded better to warming. Younger patients were more likely to demonstrate BAT (P < 0.001). No significant relationship between BAT and height, weight, or body mass index was found. The most common site for BAT visualization was the cervical region (89%), followed by supraclavicular (75%), paravertebral (50%), suprarenal (21%) and paraaortic (7%) regions. CONCLUSION: Thermal control for the reduction of BAT can achieve reductions in the incidence of BAT by as much as 78%. The reduction of BAT on PET images can reduce false-positive and false-negative results and minimize the need for rescanning.